Case of probable spontaneous regression of Merkel cell carcinoma combined with squamous cell carcinoma without surgical intervention

Abstract

Merkel cell carcinoma (MCC) is a rare but more lethal cutaneous cancer than melanoma. However, spontaneous regression of a number of MCC has been reported, although the cause of this regression remains unclear. In most cases, MCC regresses after a surgical procedure, for example, biopsy. Herein, we report a case of Merkel cell polyomavirus-negative MCC coincident with squamous cell carcinoma (SCC) that underwent true spontaneous regression without biopsy. One month after the patient's first visit, clinical examination revealed that the tumor had not grown, but its surface showed changes in texture and color. Histopathologically, the excised specimen was indicative of MCC coincident with SCC and showed extensive necrosis in the upper portion of the tumor, numerous caspase-3-positive apoptotic cells, an accumulation of CD68-positive foam cells and vascular invasion. These findings suggested that the tumor had regressed. We hypothesize that extensive coagulative necrosis resulting from an insufficient local blood supply triggered the shedding of some products or components of MCC and SCC, which in turn induced antitumor immunity against both lesions.

Case Details

Disease Location

Skin

Personal Characteristics

83-year-old japanese woman

Clinical Characteristics

Presented with a nodular lesion on the right bridge of her nose, which she had first noticed 1 year before the first visit, which had gradually enlarged. Clinical examination revealed a 20- mm, reddish, firm, non-ulcerated nodule. One month after the first visit, a second examination revealed that the tumor had shrunk slightly and was wrinkled and crusted. The patient underwent surgical resection of the tumor without radial margins. Histopathological examination of the excised specimen revealed: (i) merkel cell carcinoma (mcc) coincident with squamous cell carci- noma (SCC) but without a transition zone; (ii) extensive coagulative necrosis on the surface (iii) a high proportion of apoptotic cells and low mitotic activity in the mcc; (IV) an accumulation of macrophages; and (v) vascular invasion. Immunohistochemically, the dermal neoplastic cells were strongly positive for cytokeratin (ck)20, CD56, chromogranin a (cga) and neuron-specific enolase but negative for thyroid transcription factor-1 (ttf-1), leukocyte common antigen (lca) and s100. The superficial portion of the tumor showed an extensive coagulative necrotic change. The ghost cells of the necrotic tissue were immunoreactive for CD56, cga and epithelial membrane antigen (ema), suggesting that the necrotic tissue derived from mcc. The mcc was surrounded by stroma, which was composed of foam cells with a large, pale cytoplasm and a small nucleus that stained strongly for CD68. This patient received surgery alone

Remission Characteristics

Histopathological examination of the excised specimen revealed: (i) merkel cell carcinoma (mcc) coincident with squamous cell carci- noma (SCC) but without a transition zone; (ii) extensive coagulative necrosis on the surface (iii) a high proportion of apoptotic cells and low mitotic activity in the mcc; (IV) an accumulation of macrophages; and (v) vascular invasion.

Treatment & Mechanisms

Proposed Remission Mechanisms

We hypothesized that the regression was related to anatomical factors, as the dorsum of the nose is anatomically unique in several ways. The relative scarcity of subcutaneous soft tissue, a low vascular density and the sharply elevated bone at this site possibly prevented sufficient blood flow, thus averting mcc enlargement

Clinical Treatment

Biopsy surgery