Case Number : Case 902 - 3rd December Posted By: Guest

Basaloid follicular hamartoma (solitary type).

"Infundibulocystic" basal cell carcinoma.

Although basaloid follicular hamartoma and infundibulocystic basall cell carcinoma probably represent a spectrum of the same entity, I favor the diagnosis of the later in this case.

BCC

Basaloid follicular hamartoma

Infundibulocystic basal cell carcinoma

Slightly favour BFH. We found Merkel cells could be identified in cases we have seen. CD10 was not helpful for this differential.

I will call this infundibulocystic BCC. There is considerable mucin in the stroma (Fig 6). According to Dmitry Kasakov text book of adnexal tumors, lots of confusion exists in the differentiation between ICBCC and BFH, but his description of BFH, lacks any mention of cystic structures or mucin in the stroma... Lovely case :-))

[size=4][color=#000000][font=Arial, sans-serif]I don't feel comfortable with this lesion. It has some findings of malformative proliferation of distorted hair follicles, hence the name basaloid follicular hamartoma, and some findings of benign neoplastic proliferation, what would drive to trichoblastoma, although no papillary mesenchymal bodies nor indisputable specific follicular stroma can be found. However, an appropriate evaluation of the last distinctive characteristic cannot be made in a shaving biopsy.[/font][/color]
[color=#000000][font=Arial, sans-serif]I didn't find malignant features to deserve the designation of basal cell carcinoma with adnexal differentiation or infundibulocystic basal cell carcinoma. Cells don't have hyperchromatic nuclei and scant cytoplasm, and there's no discernible mitotic figures nor necrotic areas. Neither artefactual retraction clefts between tumor and surrounding stroma.[/font][/color][/size]

I think this basaloid proliferation is too much extensive and is associated with too scant fibrous stroma to be a basaloid follicular hamartoma. My preference is for an infundibulocystic basal cell carcinoma.

Agree with the above excellent discussions. I slightly favor infundibulocystic BCC over BFH for this on-the-fence lesion (based on what we have to see). Notwithstanding, there is tangential orientation which may exaggerate the vertical extent of the tumor.
Terminal hairs appear rather sparse (only two in the center), as do sebaceous glands, and there is an aberrant eccrine duct running horizontally in the dermis (first image, right), suggestive of distorted adnexal architecture for a scalp biopsy. The differential diagnosis may therefore include a basaloid neoplasm associated with nevus sebaceous.

For what it is worth, I favoured a BCC