Sinus histiocytosis: It is seen in lymph nodes draining limbs, inflammatory lesions, and malignancies. Nodal extensive necrosis
Nodal granulomatous inflammation
Nodal extensive fibrosis (Connective tissue framework)
Nodal deposition of interstitial substanceThese morphological patterns are never pure. Thus, reactive follicular hyperplasia can have a component of paracortical hyperplasia. However, this distinction is important for the differential diagnosis of the cause. Diagnosis
In cervical lymphadenopathy (of the neck),  it is routine to perform a throat examination including the use of a mirror and an endoscope.On ultrasound, B-mode imaging depicts lymph node morphology, whilst power Doppler can assess the vascular pattern. B-mode imaging features that can distinguish metastasis and lymphoma include size, shape, calcification, loss of hilar architecture, as well as intranodal necrosis. Soft tissue edema and nodal matting on B-mode imaging suggests tuberculous cervical lymphadenitis or previous radiation therapy. Serial monitoring of nodal size and vascularity are useful in assessing treatment response.Fine needle aspiration cytology (FNAC) has sensitivity and specificity percentages of 81% and 100%, respectively, in the histopathology of malignant cervical lymphadenopathy. PET-CT has proven to be helpful in identifying occult primary carcinomas of the head and neck, especially when applied as a guiding tool prior to panendoscopy, and may induce treatment related clinical decisions in up to 60% of cases. Classification
Lymphadenopathy may be classified by:

Size, where lymphadenopathy in adults is often defined as a short axis of one or more lymph nodes is greater than 10mm.
A parapharyngeal abscess is a deep neck space abscess of the parapharyngeal space (or pharyngomaxillary space), which is lateral to the superior pharyngeal constrictor muscle and medial to the masseter muscle. This space is divided by the styloid process into anterior and posterior compartments. The posterior compartment contains the carotid artery, internal jugular vein, and many nerves. Signs and symptoms
Symptoms include fever, sore throat, painful swallowing, and swelling in the neck. An anterior space abscess can cause lockjaw (spasm of jaw muscle), and hard mass formation along the angle of the mandible, with medial bulging of the tonsil and lateral pharyngeal wall. A posterior space abscess causes swelling in the posterior pharyngeal wall, and lockjaw is minimal. Other structures within the carotid sheath may be involved, causing rigors, high fever, bacteremia, neurologic deficit, or a massive haemorrhage caused by carotid artery rupture. Cause
Infection can occur from:

Pharynx: acute and chronic infection of tonsil and adenoids
Teeth: dental infection occurs from lower last molar tooth
Ear: Bezolds abscess and petrositis
Other space: infection of parotid retropharyngeal space
External trauma: penetrating injuries of neck, injection of local anaesthetic

Epidemiology
Parapharyngeal abscess is more common in male than the female gender. Any age group can develop a parapharyngeal abscess but it is most commonly seen in children and adolescents. Adults who are immunocompromised are also at high risk. == References ==