Incidental diagnosis of medullary thyroid carcinoma due to persistently elevated procalcitonin in a patient with COVID-19 pneumonia: A case report

Table 1 Serial measurements while hospitalized and first follow-up of white blood cell count, procalcitonin, C-reactive protein, and D-dimer levels

Day from admission	WBC, cells/µL	Pct, ng/mL	CRP, mg/L	D-dimer, ng/mL
2	11650	9.52	16.44	775.84
5	4690	8.94	25.92	890.35
8	8070	9.42	3.52
12	12400	9.82	3.31	456.61
16	8240	11.6	3.08
19 (Discharge)		13.1	2.71
24	3720	16.69	2.77	0.14
50	5850	16.21	0.67

CRP: C-reactive protein; Pct: Procalcitonin; WBC: White blood cell count.

Table 2 Differential diagnoses of increased procalcitonin

Bacterial infection or sepsis

Medullary thyroid carcinoma

Acute respiratory disease syndrome

Pulmonary neuroendocrine hyperplasia

Aspiration pneumonia

Small cell or non-small cell cancer of the lung

Carcinoid tumor

Other neuroendocrine tumors

Breast cancer