These findings are consistent with left breast gynecomastia.

Gynecomastia refers to enlargement of the male breast and is the most common male breast abnormality. It occurs most commonly in adolescent boys and older men men (>50 years). It has a variety of causes including drugs, functioning testicular tumors, liver cirrhosis. It's known to commonly be unilateral or assymetrical bilateral in location.

In this case, the main differential diagnosis would be male breast carcinoma. However, the perfect subareolar location and classic flame-shaped density of the lesion exclude malignancy, which would otherwise be more eccentric in location, irregular in shape and may show ill-defined or spiculated margins. Also male breast carcinoma is very rare and has higher mean age (around 70 years).