CD34 and BerEP4 Are Helpful to Distinguish Basaloid Tricholemmoma From Basal Cell Carcinoma

Follicular (Infundibular-Tricholemmal) Squamous Cell Carcinoma: A New WHO Entity. Clinicopathological Features in 103 Cases, Including Follow-Up and Implications for Patient Management

AIMS

Cutaneous follicular (infundibular-tricholemmal) squamous cell carcinoma (FSCC) is a new World Health Organization entity. We present the largest series of published cases, summarizing clinical data, diagnostic criteria, differential diagnosis, and implications for patient management.

METHODS

Cases were identified from 2004 to 2011. Inclusion criteria included discrete attachment(s) of the tumor to the overlying epidermis via follicular infundibula, tricholemmal keratinization, and cellular pleomorphism. Keratoacanthoma and lesions with adjacent bowenoid epidermal dysplasia were excluded.

RESULTS

One hundred three cases of FSCC identified. 48.5% demonstrated completely circumscript borders ( in situ for practical purposes), 12.6% uncertain for invasion (overwhelmingly pushing borders), and only 38.8% as clearly invasive. Follicular mucin in acantholytic spaces within tumor epithelium was a distinctive finding in 57.2% of cases. Clinical data indicated predominance in elderly (median 78.5 years) men (70.4%), with preferential head and neck location (81.6%). Many were clinically suspected as squamous cell carcinoma (48.5%). However, a significant minority were clinically diagnosed as basal cell carcinoma (40.8%). This may reflect that FSCC commonly presented as a papule or nodule (51.3%). By contrast, keratoacanthoma was less frequently suggested (17.2%) and still fewer lesions were suspected to be actinic keratosis/Bowen's disease (13.6%). Follow-up in 82 cases (median 26.5 months, range 3-144) identified 5 (6.1%) local recurrences. There was no instance of metastasis in the subgroup of lesions with completely circumscript borders. Three of 45 (6.7%) patients, with follow-up, considered to have tumors with invasive pushing, and/or infiltrative borders developed lymph node metastases.

CONCLUSIONS

FSCC is identified as a common skin cancer, incorporating historical entities, such as infundibular carcinoma and tricholemmal carcinoma, with readily identifiable histologic features. Correct diagnosis has implications for patient management; a significant subgroup of lesions show completely circumscript borders that are considered in situ for practical purposes.

Use of Cytokeratin 17 in the Differentiation Between Desmoplastic Trichilemmoma and Cutaneous Basal Cell Carcinoma

ABSTRACT

Desmoplastic trichilemmoma (DTL) is a variant of trichilemmoma characterized by a prominent desmoplastic stroma that may mimic invasive carcinoma. These lesions typically show features of a conventional trichilemmoma at the periphery, surrounding dense hyalinized stroma with entrapped cords of tumor cells. On a small or superficial biopsy, DTL may pose a diagnostic challenge in distinguishing this benign adnexal neoplasm from invasive carcinoma, particularly basal cell carcinoma (BCC). We aimed to investigate whether the immunohistochemical expression of cytokeratin 17 (CK17) would be useful in the differentiation between DTL and BCC. CK17 is expressed in normal adnexal structures and has been shown to demonstrate strong staining in BCCs. Expression of CK17 was examined in 23 cases of DTL and 23 BCCs. An immunoreactivity score was assigned using the percentage of tumor cells staining with scoring as follows: 0, complete negativity; 1, < 15% tumor cells staining; 2, 15%-84% tumor cells staining; and 3, >85% staining. All cases of BCC scored as 3, whereas 18% of DTL scored as 3. The mean percent staining for CK17 was significantly higher for BCCs (97% of tumor cells) than DTLs (57% of tumor cells); P < 0.001 in the unpaired t test. The pattern of CK17 staining may also help differentiate between cases scoring 3. All BCCs showed strong diffuse staining throughout, whereas for those cases of DTL with a score of 3, the peripheral basaloid rim in the tumor lobules did not stain. CK17 is a useful adjunct in distinguishing DTL from BCC in small or superficial biopsy specimens.

Current Diagnosis and Treatment Options for Cutaneous Adnexal Neoplasms with Follicular Differentiation

Neoplasms derived from follicular tissue are extremely rare. Clinically, they are reported as non-symptomatic, slow-growing nodules. These lesions are mainly benign, but the malignant type can occur. Mainly middle-aged people (50-60 years of age) are affected. These carcinomas are mainly localized on the head and neck or torso. They can be locally aggressive and infiltrate surrounding tissue and metastasize to regional lymph nodes. In the minority of cases, distant metastases are diagnosed. Quick and relevant diagnosis is the basis of a treatment for all types of tumors. The patient's life expectancy depends on multiple prognostic factors, including the primary tumor size and its mitotic count. Patients should be referred to a specialized skin cancer center to receive optimal multidisciplinary treatment. This article tries to summarize all the information that is currently available about pathogenesis, diagnosis, and treatment methods of follicular tumors.