Residency Program - Case of the Month

History:

The patient is a 2.5 year old male, who presented with a slow growing papule on the right anterior thigh; first noticed around one year of age. The papule had occasional bleeding  but no ulcer noticed at the time of examination.

Microscopic Description:

Sections (fig 1) showed a polypoid nodule with variable atrophy and epidermal hyperplasia containing a diffuse predominantly dermal proliferation of atypical pigmented epithelioid melanocytes. Within the epidermis there was focal pagetoid upward scatter of melanocytes. Within the dermis, sheets of compact nests and strands of atypical large epithelioid melanocytes extended to a maximum depth of approximately 11.0 mm from the overlying stratum granulosum to the biopsy base.  Mitotic Index: > 6 per square millimeter; Ulceration was absent; Vascular invasion was not identified; Regression was not identified; Satellite nodule(s): was not identified; Pathologic stage: pT4a (AJCC 7th Ed.)

Two of three sentinel lymph nodes were positive for the tumor cells.

 
Figure 1

What is the diagnosis?

A)  Atypical spitz tumor
B)  Spitz nevus
C)  Nodular melanoma
D)  Spitzoid melanoma of childhood

Answer

History:

The patient is a 64-year-old female with an unremarkable past medical history who presented for evaluation of a slow growing swelling on the floor of her mouth. Physical examination revealed a firm mass (2.7 x 1.1 cm) that appeared confined to the right side with normal overlying mucosa.  A CT soft tissue scan of the neck with contrast revealed a 2.1 x 1.4 x 1.6 cm mass (Figures 1 and 2) on the right anterior floor of mouth which extended anteriorly across the midline by 5 mm, without definite invasion of the mylohyoid or right mandible, and with possible invasion of the right sublingual salivary gland. Small bilateral lymph nodes in levels 1 and 2 were identified without necrotic adenopathy.

Figure 1	Figure 2

A subsequent biopsy of the mass was consistent with carcinoma. The patient was taken to surgery for an anterior floor of mouth resection with bilateral neck dissection and radial forearm free-flap reconstruction. Intraoperative frozen section analysis of the margins of the right posterior floor of mouth, proximal lingual nerve, and level 2 lymph nodes were negative for carcinoma. Permanent histopathology revealed a single, bilateral tumor focus with no evidence of perineural or lymphovascular invasion, and of 28 lymph nodes examined, 0 were involved. The tumor was well-encapsulated and present 1 mm away from the nearest surgical (superior) margin. Pathologic staging was T2N0M0. The patient was doing well without recurrence one month after follow-up with only mild dysarthria.

Gross

Received in formalin, labeled with the patient's name and unit number, and undesignated, is an oriented 4.6 x 3.0 x 1.8 cm specimen with a suture designating the left side. The specimen consists of mucosa anteriorly (4.0 x 1.1 x 0.3 cm) and posteriorly attached irregular and roughened circular soft tissue (3.2 x 1.8 x 1.5 cm). The inferior surface is inked blue, and the soft tissue superior surface is inked black. Externally on the mucosal surface is a polypoid mass (1.1 x 0.6 x 0.4 cm) covered with mucosa present 0.6 cm from the anterior mucosal margin, 0.8 cm from the left mucosal margin, and 0.8 cm from the right mucosal margin. Cut sectioning reveals a well circumscribed tan white firm lesion (2.2 x 1.2 x 0.8 cm) without necrosis that abuts the superior margin and comes to within 1 mm of the inferior margin, and is present 0.6 cm from the anterior margin. There is a satellite nodule present (0.3 cm) covered with mucosa 0.4 cm from the right mucosal margin. The specimen is totally submitted.

Figure 3

Microscopic Images

Histologically, the tumor was composed of a poorly lobulated architecture with an intact overlying squamous mucosa and capsule (Figures 4 and 5), composed of cohesive sheets of an atypical monotonous population of infiltrating epithelial-like cells without surrounding desmoplasia. The tumor cells had vesicular nuclei with prominent nucleoli, mild to moderate lightly eosinophilic cytoplasm with ill-defined cell borders. Dispersed in the background were numerous lymphocytes and plasma cells (Figures 6 and 7).  Abundant mitotic figures, keratinization, and necrosis were not identified.

Figure 4		Figure 5
Figure 6		Figure 7

Immunohistochemistry

EBER-ISH: Negative

Answer