Mohs micrographic surgery in rare cutaneous tumors: a retrospective study at a Brazilian tertiary university hospital

Abstract

Background: Mohs micrographic surgery is an established technique in the treatment of cutaneous neoplasms. It offers higher cure rates and the main indications are non-melanoma malignant skin tumors. Few studies have been performed on the treatment of rare tumors through this technique.

Objective: To study rare skin tumors and rare variants of basal cell carcinoma and squamous cell carcinoma submitted to Mohs micrographic surgery in a tertiary service in relation to frequency, disease-free evolution, and applicability of this surgical procedure for this group of tumors.

Methods: This was a retrospective observational study including rare skin tumors and less common variants of basal cell carcinoma and squamous cell carcinoma treated using Mohs micrographic surgery, between October 2008 and April 2021.

Results: During the study period, 437 tumors were treated using Mohs micrographic surgery, and 22 (5%) rare skin tumors were selected. The tumors comprised three dermatofibrosarcomas protuberans, two atypical fibroxanthomas, two spiradenomas, two hypercellular fibrohistiocytomas, one primary cutaneous adenocarcinoma, one trichoblastoma, one porocarcinoma, one chondroid syringoma, one cutaneous angiosarcoma, one Merkel cell carcinoma, and one sebaceous carcinoma. Six other cases of rare basal cell carcinoma variants with trichoepitheliomatous differentiation, metatypical basal cell carcinoma, and clear cell squamous cell carcinoma were included. There were no cases of recurrence after an average of six years of follow-up.

Study limitations: This is a retrospective study on rare neoplasms carried out in a single referral center, and this surgical technique isn't widely available in the public service.

Conclusion: This retrospective case series showed that Mohs micrographic surgery is an appropriate treatment for rare skin tumors. They corresponded to 5% of the tumors treated by the technique during a 12-year-period, with no recurrences identified.

Keywords: Acrospiroma; Adenocarcinoma; Carcinoma, Merkel cell; Dermatofibrosarcoma; Mohs surgery; Skin neoplasms.

Figure 1

Number of stages required for complete tumor excision according to the diagnosis or treated lesion.

Figure 2

Dermatofibrosarcoma protuberans (Paraffin-embeded section, Hematoxylin & eosin). (A) (top left image): recurrent neoplasm, invading the hypodermis on the right side of the image and, on the left, an area of cicatricial fibrosis and granulomatous foreign body reaction secondary to previous conventional surgery. (B) (top right image): dense area of storiform pattern. (C and D) (bottom right and left images): infiltrative periphery of the neoplasm, with fascicles of monomorphic spindle cells, invading fibroconnective tissue on the left, and adipose tissue in both. Source: Archives of Dermatology/Pathological Anatomy HC-Unicamp.

Figure 3

Recurrent trichoblastoma. (A) (top image: clinical delimitation during MMS. (B) (lower image (paraffin-embedded section, Hematoxylin & eosin): proliferation of follicular germ cells forming, islets of basaloid cells inside a fibrocellular stroma. Source: Archives of Dermatology HC-Unicamp.

Figure 4

Nodular lesion measuring approximately 1.5 cm below the eyelid with a diagnosis of primary cutaneous adenocarcinoma. Source: Archives of Dermatology HC-Unicamp.

Figure 5

Primary cutaneous adenocarcinoma (Hematoxylin & eosin). (A) (image on the left): 5 micron-thick frozen sections, showing glandular structures infiltrating the reticular dermis, associated with chronic inflammation. (B) (center image): paraffin-embedded section showing neoplastic perineural infiltration. (C) (image on the right): paraffin-embedded section, panoramic view showing a poorly circumscribed tumor, consisting of irregular glandular structures invading the dermis. Source: Archives of Dermatology/Pathological Anatomy HC-Unicamp.

Figure 6

(A) Scar on the right leg secondary to previous conventional surgery. (B) Clinical delimitation of recurrent spiradenoma during MMS. Source: Archives of Dermatology HC-Unicamp.

Figure 7

Spiradenoma (5-micron thick frozen sections stained with Hematoxylin & eosin). (A) (image on the left): multinodular pattern, with relatively large and circumscribed nodules within the dermis and subcutaneous tissue. (B) (image on the right): Basaloid cells of two types. In the periphery they are small with hyperchromic nuclei and in the center or around small lumens they are larger with pale nuclei. Source: Archives of Dermatology/Pathological Anatomy HC-Unicamp.

Figure 8

(A) Image on the left: Extraocular sebaceous carcinoma. (B) (Upper right image (paraffin-embedded section): poorly defined lobes of basaloid cells and poorly differentiated sebaceous cells. Moderate atypia. (C) (lower right image 5 micron thick frozen section): tumor debulking during Mohs micrographic surgery. Source: Archives of Dermatology HC-Unicamp.