Cutaneous cystic lesions have broad differentials from common benign entity to rare malignant lesions. Clinical evaluation of the lesion is the key for differentiation as some rare malignant entities may simulate benign looking lesions. High index of suspicion should be maintained for any aggressive behavior, which may require more thorough evaluation including histopathology and radiographic imaging studies. We report a rare case of cystic poorly differentiated squamous cell carcinoma (CPDSCC) of scalp. Case presentation: We report a case of a thirty seven years old Filipino expatriate gentleman who presented with a scalp swelling which was gradually increasing in size for four months and was operated upon with a working diagnosis of sebaceous cyst.
On post op excisional biopsy it turned out to be poorly differentiated cystic squamous cell carcinoma of scalp. On further workup no metastasis or other primary were found. Complete re-excision of the lesion with no evidence of residual tumor was achieved. Long term follow up was lost as patient left for native country. Discussion: Poorly differentiated cystic squamous cell carcinoma of neck is being reported as metastasis to lymph nodes from the primary residing in upper aerodiagestive lymphatic systemic but it may also appear as cystic subcutaneous lesion of scalp as primary itself or with unknown /undiagnosed primary at time of diagnosis.
Conclusion: Though cystic cutaneous lesions are very commonly encountered in clinical practice. High suspicion for malignancy should be maintained if the lesion shows any aggressive behavior. Prompt investigations should be done prior to surgery to determine the nature of disease and the most effective management of the patient. Poorly differentiated cystic differentiated squamous cell carcinoma should also be considered in the differentials of cystic cutaneous lesions that show aggressive behavior. Keywords Cystic poorly differentiated squamous cell carcinoma, trichilemmal carcinoma, malignant proliferating trichilemmal carcinoma, metastatic cystic squamous cell carcinoma, epidermoid cyst Highlighters/learning points: Cutaneous cystic lesion have wide clinical differentials High index of suspicion should be maintained when any cutaneous lesion shows aggressive behavior Prompt investigation should be carried before surgical resection, final diagnosis is provided by histopathology We report a rare case of cystic poorly differentiated SCC of scalp misdiagnosed clinically as a sebaceous cyst.
List of abbreviations: 1. Squamous cell carcinoma (SCC) 2. Metastatic carcinoma of unknown primary site (MCUP) 3. Proliferating trichilemmal tumor (PTT) 4. Cystic poorly differentiated squamous cell carcinoma (CPDSCC) Introduction: Cutaneous cystic lesions have a wide clinical differentials diagnoses ranging from a common benign sebaceous cyst to rare metastatic carcinoma of unknown primary site (MCUP).1 Most of the cystic lesions are diagnosed on the basis of clinical presentation including history and examination but the definite diagnosis is provided by histopathology. Sometimes it is not possible to differentiate benign from malignant lesion on the clinical basis. In such cases further investigation such tissue biopsy and radiological examinations are required to narrow the clinical differential diagnosis. We are reporting a case of a cystic poorly differentiated squamous cell carcinoma to emphasize the importance of keeping a high suspicious of malignancy in dealing with cutaneous cystic lesion and the importance of preoperative assessment in such lesions.
Case presentation: We report case of a 37 years old previously healthy expatriate male, who presented to emergency department with scalp swelling for four months. The swelling was gradually increasing in size associated with mild pain. He had no history of trauma, fever, weight loss or any other associated symptoms. Past medical, surgical and family history was negative for any malignancy. He was nonsmoker, nonalcoholic who worked as a laborer. On examination there was a solitary scalp swelling (Figure 1) measuring 7x7cm in size, with crusted surface. It was spherical, smooth, sub cutaneous lesion on the back of scalp 6cm posterior to left mastoid process. The lesion was tense, freely mobile.
It was non pulsatile, non-compressible, non- reducible and was not trans illuminating. There was no clinically evident lymphadenopathy. Neck and throat examination was unremarkable. No other abnormal findings were identified. Provisional diagnosis of sebaceous cyst was made with differentiation diagnoses of dermoid cyst or scalp lipoma. CT head was done prior to surgery to rule out any intracranial extension, which showed 7x 3.6x 7.7cm subcutaneous extra cranial cystic lesion with no intracranial extension (Figure 2). Patient was posted for elective excision of scalp cyst. Intraoperative patient was found to have left parieto occipital extracranial scalp lesion with both cystic and soft tissue components, infiltrating the galea aponeurotica and surrounding muscles.
Efforts were made for complete excision of the mass, primary closure was done. The entire specimen was sent for histopathological examination. The specimen comprised of several fragments of tissue and pieces of skin. The sections showed fragments of cyst wall lined by malignant squamous epithelium with no benign epithelial component identified (figure 3 A,B,C). Foci of dermal invasion with desmoplastic stroma reaction were seen.
The histopathological differential diagnosis included a cystic poorly differentiated squamous cell carcinoma, malignant proliferating trichilemmal tumour and trichilemmal carcinoma. In view of the poorly differentiated nature of the epithelium and lack of a benign cyst component the diagnosis of cystic poorly differentiated squamous carcinoma was favored. The patient was discussed at the skin MDT. PET scan, local and neck ultrasound was performed to examine for disease extent. Re-excision and reconstruction was performed after a negative PET scan and ultrasound of the neck.
. The histopathology showed no residual tumor. Post op patient did well (Figure 4) Long term follow up was not possible as patient had left for his native country. Discussion: Cutaneous cystic lesions are very common and seen in routine daily practice. They have wide differentials from common benign lesions to rare malignant lesions.
Though most of the benign lesions are diagnosed on the basis of clinical judgment that is confirmed in the majority of the cases by post-operative histopathological examination. However, in rare cases a malignant lesion is diagnosed histologically after surgery which was initially thought to be benign. Therefore clinical suspicious for malignancy should be maintained in cases where the clinical assessment shows suspicious features or aggressive behavior such as rapid growth, large size at presentation, fixation to surrounding structures and ulceration. This will require more prompt evaluation that should include a detailed clinical history, local and systemic examination.
further investigation such as CT, MRI or PET scan can be ordered depending on the initial clinical findings to assess the extent of local disease and to rule out distant metastasis. Fine needle aspiration and tissue biopsy should be also considered when the clinical suspicious of malignancy is high. Excisional biopsy should be performed when the nature of the lesion cannot be ascertained on the initial clinical assessment. These measures must be implemented in order to establish the correct diagnosis and decide on the best way of how to manage the patient. In our case an initially begin looking lesion with a provisional diagnosis of sebaceous cyst turned out to be rare CPDSCC which can either be primary or metastatic carcinoma of unknown primary MCUP.1 The differentials diagnoses included sebaceous cyst, dermoid cyst or scalp lipoma on clinical judgment and trichilemmal carcinoma or malignant proliferating trichilemmal tumor on basis of histopathology.
Epidermoid cysts or epidermal inclusion cyst or inappropriately sebaceous cysts, are one of most commonly occurring cutaneous cysts. They can occur on any part of the body. The diagnosis is usually clinical, they appear as cystic or nodular lesion, often with a central punctum, and upon palpation the lesion is freely mobile, lesion greater than 5cm are rare. The diagnosis can be confirmed by histology. Malignant transformation can occur, although its rare but transformation into Basal cell carcinoma, squamous cell carcinoma(SCC )2, melanoma, Bowen’s disease, Paget disease have been reported.
Based on 13 reported cases, Anton Badiola et found that mean age at presentation of SCC arising from epidermal inclusion cyst was 43.2 years.3. They also found that it is more common in men, mostly occurring in head and neck region and the mean diameter was found to be 5.7cm. No established risk factor are known, but possible triggering factors such as sun related skin damage, human papilloma virus have seen suggested.3 Trichilemmal carcinoma is a rare malignant skin tumor with approximately 100 cases reported 4. On histopathology they show significant overlap with clear cell squamous cell carcinoma.
5They are common on sun-exposed surfaces of older adult patients. 6 The tumor is composed of infiltrative aggregations of pale keratinocytes with outer root sheath differentiation, cytologic atypia, and brisk mitotic activity. Although histological picture suggests a high grade malignant neoplasm, trichilemmal carcinoma has an indolent course.6 Surgical excision, with histological conformation of margins is the recommended treatment. Mohs micrographic technique can be considered where tissue sparing or cosmoses is important 4. In a review of 35 cases with follow-up data, local recurrence occurred in 3 cases and metastatic disease in 1 after an average follow-up of 33 months 4. Proliferating trichilemmal tumor (PTT) is a group of rare tumors with follicular isthmic differentiation and varying degree of atypia.
Malignant transformation in case of PTT is very rare. It is usually confused with squamous cell carcinoma. Only 39 well-documented cases of malignant proliferating trichilemmal cyst have been published.7The pathogenesis of malignant proliferating trichilemmal tumor was proposed by Saida et al. 8 It showed infiltrative growth, marked cytological atypia, high mitotic activity including atypical forms and lymph nodes metastasis.9 PTT showing a combination of non-scalp location, recent rapid growth, size greater than 5 cm, infiltrative growth, and significant cytologic atypia with mitotic activity can be considered as malignant PTT.9Most PTT present as solitary and asymptomatic nodules, occurring most commonly in women, in the sixth and seventh decades of life with 90 percent are found on the scalp.10Treatment includes adequate surgical excision.
The patient should be followed closely after surgery.10 In literature cystic squamous cell carcinoma is only described as metastatic cystic squamous cell carcinomas of cervical lymph nodes, with the origin of the primary site in the upper aero digestive lymphatic system.11 In the past, these cystic cancers often have been misdiagnosed as branchiogenic carcinomas, that is, malignant transformation of brachial cleft cyst. Today, it has been concluded that so-called branchiogenic carcinomas are actually cystic metastases in the neck arising from an oropharyngeal primary SCC.12 Lester D. R. Thompson at al 11 reviewed 136 cases of cervical cystic SCC, which included 28 females and 108 males.
They presented with neck lesion. The mean age at presentation was 54.2 years and duration of symptoms was 4.5 months on average .Follow-up was available in all cases. During the follow-up, 87 primaries (63%) were identified at the base of the tongue, the lingual tonsil region, or the faucial tonsil region,11 primaries were in the nasopharynx; 11 primaries were in the larynx, palate, or sinuses; and 27 primaries were of unknown location or as yet undiscovered. Primaries were identified from the day of the initial surgery to 11 years later. The average time to discovery of the primary was 12.4 months.
These patients underwent surgery alone or in combination with radiotherapy or chemotherapy or both. Statistics for all sub groups were provided. Five criteria were established to define the typical histologic features of the cystic SCCs in the neck: 1) formation of a large cyst or cysts; 2) with only focal areas of solid growth; 3) cystic spaces lined by a squamous epithelium arranged in a band like alignment, keeping a fairly uniform thickness and orderly polarity through the cyst, with occasional areas of either endophytic or exophytic proliferations; 4) epithelium that is mostly of a transitional nature, with the cells presenting high nuclear-to-cytoplasmic ratio and limited keratinization, with suggestions of squamous pearl formation; and 5) no prominent degree of anaplasia, but instead repetition of the normal tonsillar crypt epithelium, with variable mitotic activity As most of the primaries were occult and small and some stayed undiscovered for several years, random biopsies or tonsillectomy were needed to identify the tumors. The primary tumor appeared histologically similar to that of the metastatic lesion.
Thorough physical examination under anesthesia with panendoscopy, comprehensive radiographic studies should be done. If even after a comprehensive clinical evaluation and investigation, the primary could not be found, it is still reasonable to assume that the primary origin is the Waldeyer’s tonsillar ring, and it is suggested for purposes of treatment, prophylactic lingual and faucial tonsillectomy, specifically on the ipsilateral side, should be considered. This retrospective study showed that this type of carcinoma appears to have a more indolent growth behavior compared with most SCCs. The survival at 5 years was found to be 77%. And it was concluded that with the identification of primary, patients can be treated relatively conservatively with surgical excision and subsequent field-limited radiation therapy.11 Regarding the mechanism of formation of cystic SCC it is postulated that most of these metastatic cystic SCC to lymph nodes are pseudocysts.
Though, some are true cystic cavities. There is strong evidence regarding formation of true cystic metastatic SCC to cervical lymph nodes that advocates the origin from salivary ducts.13 It has been noted that nodal metastases from HPV-related SCCs of the upper aerodigestive tract are prone to be cystic 1314. In another study it was found that in 121 adult patients presented with an initial diagnosis of lateral cervical cyst. Metastatic cystic squamous cell carcinoma was demonstrated histologically after surgical excision in 12 patients. The incidence of malignancy was significantly greater in patients greater than 40 years of age.
Results of preoperative fine-needle aspiration (FNA) were negative for malignancy in five cases of metastatic squamous cell carcinoma. Panendoscopy with directed biopsies revealed an occult primary in the base of tongue in three patients, tonsil in one patient, and nasopharynx in one. No primary was found in six patients, despite repeated examinations and close follow-up.15 In our case the cyst is lined by a poorly differentiated squamous epithelium with no specific lineage. Tricholemmal carcinoma has been considered but they are no specific histological or immunohistochemical features to consolidate this diagnosis.
The other diagnosis considered was malignant proliferating tricholemmal cyst, an entity that believed to be a variants of squamous cell carcinoma by Ackerman and Colleagues.16 A believe that has been disputed by other dermatopathologists and did not receive a wide acceptance. 17 In view this and the poorly differentiated nature of the cyst lining a diagnosis of cystic poorly differentiated squamous cell carcinoma. This rare variant of squamous cell carcinoma diagnosed as cystic poorly differentiated SCC, presented as scalp lesion, rapidly growing in a patient with no established risk factors for SCC. It was excised completely with further work up showing localized cystic SCC of scalp which may itself be primary or metastatic with unknown/undiscovered primary at the time of diagnosis.
There was no distant or local metastasis and no vascular or lymphatic or neural invasion. In the view of literature review some further investigation such as pan endoscopy should have been performed but as the case is of very atypical presentation, the actual course of investigation cannot be established or rationalized. It had no early re occurrence. But as the follow up was lost, prognosis after the surgical excision cannot be established. Conclusion: We report a very rare case of cystic poorly differentiated squamous cell carcinoma of scalp. It is important to consider this entity during clinical evaluation of unusual cutaneous cystic lesion. Any cutaneous cystic lesion should be thoroughly evaluated clinically for malignant features. Any lesion showing suspicious behavior such as rapid growth, large size at presentation should be further investigated with imaging and tissue biopsy. This approach would help in deciding the best management for the patient.
Declaration: 1. Ethics approval and consent to participate This case report was provided ethical approval and consent to participate by AHATH, Hamad, Qatar. Consent for publication Inform consent was taken from the patient and is attached separately. Availability of data and material All data generated or analyzed during this study are included in multiple published articles, the links to which are reported and can be assessed through the references. The authors declare that they have no competing interests. Authors’ contributions Each author provided valuable contribution to the report including from the idea, materials used, methodology, design, review and final assembly of the paper. Acknowledgments We acknowledge the support of department of surgery, pathology and research, HMC, Qatar for their support and encouragement. Funding This case report did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
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