A Rare Tumor at an Unusual Site with a Rare Association

Case Report

A 23-year-old female presented with an asymptomatic, pinkish growth on the inner aspect of left thigh of 15-year duration. The lesion was initially pea-sized and progressively grew over time. At presentation, there was a one-year history of rapid growth of lesion associated with watery discharge. On examination, there was a presence of non-tender pink to erythematous, polypoidal soft tissue growth measuring approximately 3 × 2 × 1 cm on the inner aspect of upper one-third of left thigh, with perilesional hyperpigmentation and mild serous discharge. The surface was partially eroded. Rest of the cutaneous examination was normal. Excisional biopsy was performed [Figures 1-4].

Figure 1.

Erythematous, polypoidal growth on left thigh, with perilesional hyperpigmentation, mild serous discharge, and partially eroded surface

Figure 4.

(a) Lobules of tumor cells composed of variable sized ducts lined by apocrine cells, few of them having secretion lined by flattened epithelium (H and E, 40x). (b) The surrounding stroma was thick and fibrotic. (H and E,100x)

Figure 2.

Dermoscopy revealed papillomatous projections with grape-like clusters in a floriform pattern. They were milky-white to reddish at the periphery and reddish at the base. Multiple polymorphic vessels with pinkish white rim were seen within the clusters with a single focal area of ulceration ((DermLite II, polarized, 10x)

Figure 3.

(a) The tumor tissue was covered by stratified squamous epithelium exhibiting papillomatosis, acanthosis, spongiosis, and interface reaction. Deeper tissue showed multiple papillae lined by epithelium showing apocrine glandular feature (H and E,10x). (b) The stroma was made of multiple congested delicate capillaries and inflammatory cells, predominantly plasma cells (H & E, 40x)

What is the diagnosis?

Answer

Syringocystadenoma papilliferum (SCAP) with tubular apocrine adenoma (TAA).

Discussion

SCAP is a rare benign sweat gland tumor that occurs most commonly in childhood or adolescence.[1] It may be solitary or multiple with variable morphology in the form of linear, translucent or pinkish papules, plaques, nodules, or tumor of varying size.[1,2] The surface may be flat, verrucous, or papillomatous.[2] The size enlarges at puberty, and it becomes crusted and papillomatous. Although it is most common on the face and scalp, other areas of the body (trunk, genitals, and extremities) may be affected in 25% of the cases.

SCAP usually arises in a pre-existing nevus sebaceous. It may or may not occur in association with other skin conditions. Its association with TAA was first described in 1987 by Toribio et al.[3]

The commonest dermoscopic pattern described in association with SCAP is a symmetric erythematous lesion with “exophytic papillary structures.” Others include central depression with yellowish-white discoloration, ulceration, and variable morphology of vessels (which may be irregular dotted, glomerular/linear vessels, hairpin vessels, polymorphous vessels, or comma shaped vessels with a surrounding pinkish-white rim). Although the dermoscopy of TAA is unclear, the coexistence of short fine telangiectasias and large blue-gray ovoid nests arranged in a floriform pattern was noted to be suggestive dermoscopic finding in TAA.[4]

On histopathological examination, SCAP usually shows multiple cystic invaginations in fibrous tissue background. Keratinizing squamous epithelial cells line the upper potions of cystic invaginations, whereas glandular epithelium lines the lower regions, which contain papillary projections. These papillary projections are the most characteristic pattern.[2] SCAP and TAA exhibit overlapping histopathology as observed in the study by Kazakov et al.[5]

With reference to the current case, the histopathological feature of the presence of papillae in the deeper layers of dermis with connective tissue and plasma cells represents SCAP, while the lobules of tumor cells composed of variable sized ducts lined by apocrine cells with apocrine features (decapitation secretion) are features of TAA and are not seen in SCAP.

Although rare, the transition of SCAP to basal cell, ductal or metastatic malignancy has been reported. 10% of the cases progress to basal cell carcinoma. Therefore, excisional biopsy, which is the only treatment of SCAP, was done in our patient, which also confirms the diagnosis.

Only 13 cases of co-existence of SCAP with TAA have been described in the literature, with only three cases occurring without pre-existing nevus sebaceous.

This case is unusual considering its location outside the scalp region and occurring de novo in an adult patient without a pre-existing nevus sebaceous.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.