Lymphoma includes a set of malignant solid tumors originating from lymphatic hematopoietic tissues. The lesions are wide ranging, their pathological characteristics are variable, their classification is complex and imaging diagnosis is difficult. Precursor T-cell lymphoblastic lymphoma (T-LBL) is a rare type of malignant lymphoma, with manifestations including lymph node enlargement, hepatosplenomegaly and annular erythema (1). The nasal mucosa, tonsils, oral cavity, skin, small intestine, or mediastinum may be involved in T-LBL (2); however, extensive involvement of the mediastinum, pleura and pericardium is rare (3–6). This is the case report of a T-LBL extensively involving the mediastinum, pleura and pericardium in a 54-year-old woman. The patient was diagnosed with malignant lymphoma following positron emission tomography/computed tomography (PET/CT) imaging. A subseqent biopsy according to the PET/CT images confirmed the diagnosis of T-LBL.

The patient was a 54-year-old woman, complaining of anhelation, chest tightness and tiredness for ~3 months, without palpitations or chest pain. The patient had no history of tuberculosis, hepatitis, or other communicable diseases. Following admission, the biochemical tests revealed a serum potassium level of 2.93 mmol/l, a blood chlorine level of 84 mmol/l and a serum albumin level of 30.6 g/l. In addition, the purified protein derivative-immunoglobulin G was negative and the concentration of cancer antigen 125 in the serum was 99.2 U/ml. Color doppler echocardiography revealed a massive pericardial effusion and a chest CT scan revealed a diffuse mass of soft tissue density involving the mediastinum, accompanied by pleural thickening, pericardial thickening, pleural effusion and pericardial effusion. The mass surrounded the trachea and the blood vessels in the mediastinum. On contrast-enhanced CT, the thickened pleural and pericardial mass was slightly to moderately enhanced. Several thoracocenteses indicated inflammatory changes and the cytological examination of the pleural fluid and conventional pleural biopsy under CT guidance (performed twice, tissue block size 3×8 mm and 3×10 mm, respectively) identified no heterotypic cells. Although on ¹⁸F fluorodeoxyglucose (FDG) PET/CT imaging the lesions exhibited a moderate FDG uptake, with a maximum standard uptake value of 4, a diagnosis of malignant lymphoma was considered. Based on the PET/CT images that showed an active site, a biopsy guided by PET/CT was performed and a pathological tissue sample of ~3×15 mm was removed. On microscopic examination (hematoxylin and eosin staining), the lesion was composed of numerous middle-sized lymphocytes with a diffuse distribution pattern. The immunohistochemical results were as follows: CD2⁺, CD3⁺, CD5⁺, CD7⁺, TDT⁺, CD99⁺, CD10⁺, CD8⁺, Ki67⁺ (~80%), CD4⁻, UCHL1⁻, TIA⁻, Granzyme-B⁻, CK⁻, CK19⁻, CD20⁻, CD21⁻ and CD23⁻. The comprehensive hematoxylin and eosin stain morphology and the immunohistochemical results confirmed the diagnosis of T-LBL.

Oral and written consent was obtained from the patient prior to all the invasive interventions. Since all such interventions are for clinical routine inspection or treatment, the present study was exempt from medical ethics review.

Lymph cell lymphoma was first described in detail in 1916 by Sternberg (http://reedsternbergcells.org/helpful-information-about-reed-sternberg-cells). In 1973, Smith (7) reported that lymphoblastic lymphoma originated from thymus lymphocytes. Barcos and Lukes (8) described a ‘nuclear lymphoid cell lymphoma’, which was officially named ‘lymph cell lymphoma’ in 1975. Currently, the World Health Organization refers to the T-cell-derived lymphocytoblast lymphoma as ‘T-LBL’ (9).

T-LBL is a rare malignant lymphoma. The median age at onset for T-LBL is 16 years (range, 4–84 years). Children and adolescents are the most vulnerable, accounting for ~30–40% of all cases of T-LBL, with only 3–4% of the patients being adults. The male:female ratio is reported to be 2.5–3:1 (10). The typical clinical manifestation of diaphragmatic lymph node enlargement is accompanied by local oppression and systemic lymphoma symptoms. The tumor often grows quickly in the anterior mediastinum (50–80%) and may infiltrate the central nervous system, the gonads and even the bone marrow. The clinical manifestations in our patient were mainly diffuse nodules in the mediastinum, pericardium and diaphragmatic pleura, bilateral pleural thickening and pleural and pericardial effusion. The patient was an adult female, aged 54 years and this disease exhibits a significantly lower incidence in this population; we identified no similar cases reported in relevant literature.

¹⁸F-FDG imaging may provide an important basis for the diagnosis and differential diagnosis of malignant lymphoma. Malignant lymphoma is generally characterised by a higher cell density compared to other cancer cells and, thus, several lymphomas exhibit high FDG uptake (10). Following a review of several studies, Baba et al (1) concluded that the degree of FDG uptake is largely dependent on lymphoma histology, with the aggressive type usually exhibiting higher uptake. Compared to conventional CT, ¹⁸F-FDG imaging exhibits higher sensitivity and specificity and may help prognosis and treatment.

A previous study by Reske (11) analyzed 15 studies on lymphoma, involving a total of 723 patients, and summarized the results of FDG PET imaging. The sensitivity of FDG PET imaging was reported to be 71–100%, with a specificity of 69–100% and a negative predictive value of 80–100%, whereas with CT, the specificity and positive predictive value were very low (4–31 and 19–60%, respectively). Hernandez-Maraver et al (12) analyzed 47 cases of lymphoma patients diagnosed by PET/CT imaging and compared the results to those of PET or CT imaging alone. The results of PET/CT in 11 patients (10 with Non-Hodgkin’s lymphoma and 1 with Hodgkin’s lymphoma) revealed an increase in stage (P=0.012). The PET/CT imaging detection of nodal and extranodal lesions exhibited a significantly higher sensitivity compared to the sensitivity of CT or PET imaging performed separately. ¹⁸F-FDG PET imaging may also help differentiate between lymphoma subtypes.

However, ¹⁸F-FDG PET imaging in the diagnosis of lymphomas has certain limitations. T-cell lymphomas are complicated and the majority exhibit low to moderate FDG uptake. If the nidus is too small or of low-level malignancy, this examination may yield false-negative results. In addition, inflammation, granulomas, physiological uptake by the gastrointestinal tract, urinary tract and muscle, as well as thymus and bone marrow proliferative response may be characterized as false-positives (13).

Although the patient had to undergo biopsy twice under conventional CT guidance to obtain sufficient specimens (3×8 mm and 3×10 mm), we were unable to identify tumor cells. Based on the PET/CT images that showed an active site, a biopsy guided by PET/CT was performed and a pathological tissue sample of ~3×15 mm was removed. Therefore, ¹⁸F-FDG PET/CT imaging may also guide the selection of clinical puncture biopsy sites and improve the accuracy and consequent success rates of the procedure. Although histopathological assessment remains the gold standard for the diagnosis of T-cell lymphoma, there are anthropogenic limitations, as well as limitations regarding the characteristics of the lesions per se (e.g., necrosis and inflammation) inherent in puncture biopsies (5,6). Therefore, the proper selection of the biopsy site and technique is crucial for accurate pathological diagnosis. In our patient, improper selection of the sampling position during the initial biopsy led to a misdiagnosis. Finally, with PET/CT imaging and PET/CT scan-guided puncture biopsy in the right posterior pleura led to the confirmation of the diagnosis of T-LBL. These results suggest that PET/CT scan may be clinically valuable in the selection of biopsy positions in T-LBL cases.

In conclusion, we presented a rare case of T-LBL extensively involving the mediastinum, pleura and pericardium and demonstrated that PET/CT may be of significant value in the clinical diagnosis of lymphoma and may be used as guidance for the selection of puncture biopsy sites.