Answer: A - Grade group 1

Prostatic adenocarcinoma (PCa) is the most common non-cutaneous malignancy in males in North America, and is the second most common cause of cancer death in males in the USA. A disease of the elderly (median age at diagnosis = 67 yrs.), it shows an indolent clinical course (10 year survival rate of 99%). The pathological diagnosis of PCa is based on a combination of architecture and cytomorphology. The management and outcome of the disease is closely dependent on the tumor grade (reported as Gleason score/grade group system); therefore accurate grading of PCa is very crucial.

In this case, there are irregular small crowded glands with open lumina, lined by cells with a high N/C ratio, and nuclear chromatin clumping and prominent nucleoli. There is also mucin production, both in the lumen and extravasated in the stroma. The most likely diagnosis is PCa with mucinous differentiation. Grading of mucinous PCa can be challenging due to fragmentation, artifactual complexity and presence of mucinous fibroplasia (not seen in this case). For grading of mucinous PCa, it is recommended to consider the architectural pattern regardless of mucin. Therefore this case should be graded as Gleason score 3 + 3 = 6 (grade group 1).

Cribriform architecture is defined as complex glands where the tumor cells inside the cribriform do not connect with the stroma. None of the neoplastic glands in this case meet this definition. The proper management for this case is active surveillance.