There’s a tendency in medicine to describe the size of things in the body in comparison to citrus fruit.
Thus a uterus, either pregnant or with tumours such as fibroids, might be the size of a lemon, an orange, or a grapefruit. (Once it’s bigger than a grapefruit it’s described in some other way – not as some sort of melon but in comparison to a uterus at a certain stage of pregnancy eg at 35 weeks, inclusive of baby).
Elsewhere in the body, organs aren’t naturally meant to change in size, so you’d only describe the dimensions of an abnormal mass in that way. The American neurosurgical registrar described our patient’s brain tumour today as the size of a clementine, which seems very specific. “As opposed to a satsuma?” I asked, but I think the Americans just say that to mean any generic mandarin. (The prognosis is good today, I hasten to add.)