Introduction Adrenocortical carcinoma (ACC) is a rare condition, with an incidence of 1-2 cases per million (1) and poor prognosis, with a 5-year survival of 60% for tumours confined to the adrenal gland, 35-50% for locally advanced disease and even lower, approximately 15%, for metastatic disease (2-4). ACC may be asymptomatic and diagnosed incidentally or present with unspecific symptoms due to local tumour growth or appear with a hormonal syndrome, most commonly with Cushing’s Syndrome or mixed Cushing’s syndrome and virilization, whereas feminization and Conn’s Syndrome occur rather rarely (5). Case report We herein report an unusual case of a 74-year-old woman (study approved by the Scientific Committee of “Laiko”-University-Hospital, audit number: 1108/22-01-2021) who presented to our outpatient clinic with pronounced facial hirsutism of recent onset and a large adrenal mass. The case presented a diagnostic challenge as her clinical appearance was inconsistent with the histological diagnosis. Besides from a fracture, due to an accident five years ago, the medical record of the patient was blank. She had menarche at the age of 13 years, regular menstruations every 28-30 days, with a duration of 3 days, reported dysmenorrhea and a first trimester abortion at the age of 38. The patient had no other pregnancies in her obstetric history. She had a smoking history of 5 pack/years. Upon clinical examination she presented whole-body lanugo, developed within the past two months, which was much more pronounced in the face area. Furthermore, muscle weakness of the lower extremities was observed, and a large goiter was palpable. At presentation, the patient weighted 52 kg (BMI 23.4 kg/m2), with a sitting blood pressure of 145/92 mmHg (pulse 85/min), and a female adipose tissue distribution. At the time, she empirically received 40 mg pantoprazole and 10 mg domperidone daily, due to undiagnosed gastric symptoms. Upon admission, the patient had normal serum sodium (142 mmol/l), slight hypokalemia (3.3 mmol/l) and normoglycemia (87 mg/dl). The biochemical tests did not identify any particular abnormalities. Hormonal evaluation showed low or low-normal androgen values (Dehydroepiandrosterone (DHEA), DHEA-Sulfate, ?4-androstenedione, 17-OH-progesterone, free testosterone index), with an only slightly insufficient cortisol suppression upon overnight dexamethasone test (2.17 µg/dl) and a normal adrenocorticotropic hormone (ACTH) value. Luteinizing (LH) and follicle-stimulating hormone (FSH) were within the normal range for postmenopausal women. The aldosterone-to-renin ratio (ARR) was also slightly increased. Thyroid stimulating hormone (TSH), fT4 and calcitonin were within the normal range (Table 1). Additionally, laboratory findings showed increased levels of carcinoembryonic antigen (CEA) and neuron-specific-enolase (NSE), with slightly increased levels of chromogranin A (CgA). In parallel, the bone-mineral-density of the left femoral neck was compatible with severe osteoporosis with a T-score of -3.47. Thyroid ultrasonography confirmed the presence of a large goiter with a 5 x 5 cm large nodule in the left lobe (Figure 1). A fine needle aspiration (FNA) biopsy of the thyroid nodule was performed, and the cytology revealed a lesion compatible with benign disease (The Bethesda System for Reporting Thyroid Cytopathology II). Abdominal computed tomography (CT) imaging showed a 7.8 cm large inhomogeneous mass of the left adrenal gland. One month later, in the magnetic resonance imaging (MRI), the adrenal mass measured 8.5 cm, with central necrosis. One week later, the FDG-PET/CT confirmed the presence of the lesion of the left adrenal gland, now measuring 8.9 cm, with a SUVmax of 13.5. Hypermetabolic foci with increased FDG uptake were also seen in the right upper lobe of the lung, in several lymph nodes of the right pulmonary hilum and in the soft tissue close to the right femoral neck (Figure 1). To identify the tumour origin, a CT-guided biopsy of the largest pulmonary lesion was performed. The cytological examination showed small-to-medium sized malignant cells of unknown origin (negative (-) for TFT, CD56, P63). Due to the progression rate, left adrenalectomy, nephrectomy, and splenectomy took place. The pathologists reported extensive infiltration of the adrenal gland by an undifferentiated carcinoma of unknown origin with pronounced polymorphism, nuclear atypia and high mitotic rate (52/10 HPF, ki-67: 70%, positive (+) for: CKAE1/AE3, CK8, CD10, EMA, NSE, CgA, Synaptophysin, pCEA, CDX2; weakly positive (+) for Vimentin, CK20, mCEA; negative (-) for CK7, CK5/6, P63, Thrombomodulin, TTF1, TG, GCDFP 15, RCC, S100, Mart1, CD117, calretinin, PLAP, CD30, CD5, Inhibin, HepPar1). A mitotane therapy (with dose titration from 500 mg up to 2 g/daily, and subsequently according to the mitotane plasma levels, to remain within the therapeutic window) along with hydrocortisone substitution (25 mg/daily) were directly initiated and the patient also received 6 cycles of chemotherapy (Cisplatin, Etoposide). Because of rapid disease progression, a revision of the pathology was requested. This confirmed infiltration of the adrenal gland by a solid adenocarcinoma with extensive necrosis, (ki-67>60%, positive (+) for 8.18 EMA, CEA, BerEP4, EMA, and in parts CDX2; weakly positive (+, <5%) for CgA and Synaptophysin; negative (-) for PDX1, TTF1, Inhibin, Melan A and NF). A steroidogenic factor 1 (SF-1) immunohistochemical staining was at the time not available. However, before the initiation of further treatment, the patients’ condition deteriorated quickly. Due to an episode of loss of consciousness a brain CT-scan was performed, and brain metastases were identified. Before the initiation of local radiotherapy, the patient died. Later, upon availability of SF-1 staining, this was done on the obtained slides from the resected adrenal tumour and showed very pronounced expression, supporting the suspicion of an ACC. Discussion We present here the case of a patient with clinically evident hormonal syndrome and a large adrenal mass along with extensive metastatic disease. The differential diagnosis, besides from an ACC included a primary adrenal lymphoma, a metastasis from lung carcinoma, renal cell carcinoma or carcinoma of unknown primary. From the laboratory work-up, a possibly autonomous cortisol secretion was documented, suggestive of an ACC. Still, the low normal or even suppressed androgens could not explain the prominent hirsutism of the patient. We hypothesize, that this clinical symptom originated from non-quantified steroid metabolites secreted by the tumour. Still, the ACTH and LH levels measured in this patient did not fully correspond to the expected inhibition of these two peptides. Cortisol suppression upon 1 mg dexamethasone test just exceeded the cut-off of 1.8 µg/dl, applied in our clinic with strict criteria. However, usage of different cut-offs, as e.g., 5 µg/dl is also used in clinical practice, to increase specificity of the test. Thus, a clear cortisol excess could not be documented in this patient at the time of diagnosis. It can, though, be speculated, that a cellular dedifferentiation in this rapidly progressive adrenal tumor altered the hormonal profile, while the clinical appearance of the patient could not be affected so promptly. The unilateral adrenal localization of the tumour and its large size were also suggestive of an ACC. However, the spindle-shaped intrapulmonary lesion with concurrent hilum lymph nodes raised the suspicion of a pulmonary primary. Furthermore, no clear conclusions about the origin of the tumour could be drawn from the initial pathological examination of both the pulmonary and the adrenal lesion. The presence of EMA expression, often observed in renal cell carcinomas but rarely documented in ACCs (6), and the positivity for gastrointestinal and pulmonary tumour markers, together with the absence of typical ACC markers, such as Melan A and Inhibin, questioned the diagnosis of an ACC (7). Still, the positivity for vimentin, NSE and in parts for synaptophysin and CgA were suggestive of the adrenocortical origin of the tumour. Although SF-1 can occasionally be positive in renal cell carcinomas (6), the combination of the clinical picture with the positive SF-1 staining was the crucial step to substantiate the diagnosis of ACC. This, however, was only possible post-mortem, upon audit, in the present case, whereas a respective SF-1 staining of the lung biopsy, to confirm the adrenocortical origin of the pulmonary lesions was not feasible, as no cell block was produced from the FNA, and the patient’s family had denied an autopsy. Taken together, this case underlines the difficulties in the differential diagnosis of rapidly progressive adrenal masses, and the diagnostic challenges when the clinical appearance is inconsistent with the histological analysis.