A 71 year old man presented with urinary obstructive symptoms which were clinically attributed to an enlarged prostate. Transurethral resection consisted of 18 grams of prostatic tissue with nodular hyperplasia. In addition, there were two well-circumscribed foci with a distinct histologic appearance measuring 1.8 cm in aggregate.

There is proliferation of small and medium sized acini (Fig.7.1). The acini are surrounded by cellular myxoid stroma and have a condensed rim of hyalinized connective tissue. Copious intraluminal blue mucin is seen (Fig.7.2). The peripheral basal cell layer is intact as confirmed by high molecular weight cytokeratin 34bE12 (Fig.7.3).

The differential diagnosis includes atypical adenomatous hyperplasia (Fig. 7.4), post-atrophic hyperplasia (Fig. 7.5), basal cell hyperplasia (Fig. 7.6), sclerosing adenosis (Fig. 7.7), and prostatic adenocarcinoma (Gleason 3+3=6) (Fig. 7.8).

Sclerosing Adenosis

Key Features:

• Circumscribed small acinar proliferation with or without infiltrative margins
• Compressed, distorted acini with abortive lumens; abundant mucin may be present
• Prominent myxoid cellular stroma
• Intact basal cell layer positive for high-molecular weight cytokeratin (Fig. 7.3)
• S-100 protein (Fig.7.9) and smooth muscle actin immunoreactivity (Fig. 7.10) in the basal cells indicating myoepithelial differentiation
• Rare cases show moderate to severe cytologic atypia, including nuclear hyperchromasia and enlargement, prominent nucleoli, increased mitotic activity and aneuploid DNA content
• No known malignant potential

Follow-up: The patient is alive and well without recurrent symptoms 2.5 years after the diagnosis.